Linear accelerators are typically used to generate radiation for use in medical treatment. To assist with calibration, these devices typically include a field lamp projector and/or an optical distance indicator. Field lamp projectors project a pattern of light through an optical assembly and onto the patient. The pattern of light estimates the pattern of radiation that is to be projected. Optical distance indicators project a light through an optical assembly that includes a lens having a plurality of numbers etched or printed thereon. This results in the projection of one or more numbers on the patient, which indicates to the technician a distance between the radiation generator and the patient. The light sources for these field lamp projectors and optical distance indicators conventionally include halogen bulbs, which create a large sphere of light. To try and focus the light toward the optical assemblies and to reduce reflections in the projectors, apertured plates are often arranged between the bulbs and the optical assemblies.